Design and development of a field applicable gold nanosensor for the detection of luteinizing hormone

In this paper, we describe a novel strategy for the fabrication of a nanosensor for detecting luteinizing hormone (LH) of sheep using a gold nanoparticle-peptide conjugate. A new peptide sequence "CDHPPLPDILFL" (leutinizing hormone peptide, LHP) has been identified, using BLAST and Clustal W analysis, to detect antibody of LH (sheep). LHP has been synthesized and characterized, and their affinity toward anti-LH was established using enzyme linked immunosorbant assay (ELISA) technique. The thiol group in LHP directly binds with gold nanoparticles (AuNPs) to yield AuNP-LHP construct. Detailed physicochemical analysis of AuNP-LHP construct was determined using various analytical techniques. Nanosensor using gold nanoparticle peptide conjugate was developed on the basis of competitive binding of AuNP-LHP and LH toward anti-LH. Nitrocellulose membrane, precoated with anti-LH, was soaked in the mixture of AuNP-LHP and sample of analysis (LH). In the absence of LH (sheep), anti-LH coated on the membrane binds with AuNP-LHP, leading to a distinctive red color, while in the presence of LH, no color appeared in the membrane due to the interaction of anti-LH with LH thereby preventing the binding of AuNP-LHP with membrane bound anti-LH. The sensor assay developed in this study can detect LH (sheep) up to a minimal concentration of ∼50 ppm with a high degree of reproducibility and selectivity. The gold-nanoparticle-peptide based nanosensor would be a simple, portable, effective, and low cost technique for infield applications.